1. Field
The example embodiments in general relate to a partially floating, supported offshore marine platform for supporting offshore wind turbines, bridges and marine buildings, construction methods for installing the marine platform in a marine environment, and a method of assembling the platform at a harbor site.
2. Related Art
Foundation types for offshore marine platforms may be classified into three groups: the gravity type, pile supported type, and the floating type covering water depths from shallow, medium to deep, respectively. For wind turbine and bridge structures, the horizontal forces due to wind, waves, surges and earthquakes are likely to be the controlling load cases, since the structural dead weight is small. However, this may not be the case for building structures on the offshore marine platform, as the gravity load is relatively large.
In the case where horizontal forces control the design, the use of tension piles is more effective than using ballast for the increase of dead weight of the foundation, except that the bearing stratum for the foundation is strong, i.e., bedrock, so the bearing stratum may sustain the weight of the ballasted structures. On the other hand, in the case where vertical forces control the design of the marine platform, the use of a gravity type foundation is effective if the founding layer is close to the surface of the seafloor (i.e., shallow depths), such that excavation of soft materials in the seafloor will not be in a substantial quantity. The gravity type will be advantageous; but to reduce the strength demand for the founding layer, it is desirable to either increase the contact area of the platform or reduce the loads thereon. In the case of a piled foundation, the challenges are performing piling operations at sea, as well as the construction of a pile cap for the platform in the water.